FOLLOW-UP OF INTERHEMISPHERIC DIFFERENCES OF MOTOR EVOKED-POTENTIALS FROM THE AFFECTED AND UNAFFECTED HEMISPHERES IN HUMAN STROKE

We analysed motor-evoked potentials (MEPs) from the hand muscles durin g focal transcranial magnetic stimulation (TCS) in both the affected ( AH) and the unaffected (UH) hemispheres of 17 monohemispheric stroke p atients followed-up in subacute stage. Recording sessions were perform ed at 2 (T1 session) and 4 (T2 session) months from acute stroke. Clin ical and functional scores were evaluated. An age-sex matched group of 20 healthy subjects have been referenced. In T1, relaxed MEPs from AH were smaller than UH (p < 0.001) and normals (p < 0.001). In T2, an i ncrease of AH relaxed-MEPs amplitude was observed, combined with an im provement of clinical and functional scores (p < 0.001). On the other hand, the amplitude of contracted MEPs from the AH in T1 was larger th an in the normal group. This parameter decreased toward normal limits in T2, provided that the amplitude of the MEPs from the AH improved, w hile it further increased when TCS of the AH continued to fail in elic iting MEPs. This phenomenon was statistically combined with clinical i mprovement of disability and neurological scores. Recovery of the exci tability AH threshold with progressive 'balancing' of the UH hyperresp onsiveness represents a good prognostic parameter for clinical outcome of hand motor function. (C) 1998 Elsevier Science B.V. All rights res erved.